XR500/600 cylinder head (1983-87)

By Manos, Posted February 29, 2008

Hi all,

I’m in the process of overhauling the motor of an NX 650 Dominator (same engine as the 650L).

The boy inside me demands I experiment a little bit, so I plan to (try to) install a cylinder head out of an XR500/600 (1983-87), or an XL600. That’s the one with the two individual inlet ports (and running on two carbs). I’ve read posts here and elsewhere stating that fitment may be a challenge, but it wouldn’t be fun otherwise now, would it?

I do need a bit of advise and assistance here though:

1. Would anyone know the sizes (diameters) of the inlet and outlet valves of the above engines (XR500 1983-84, XR600 1985-87, XL600 1985-87)?

2. I am told that Honda engines built after 1994 can run on unleaded fuel without risk to the valves/seats. Are there any valves/seats for the older heads that can run on unleaded?

3. Would anyone have one of those heads for sale? I’d want them complete with innards (valves, seats, guides, cam, valve cover etc etc etc) and carbs if possible.